Effects of physical restraint and endogenous adrenocorticotropin challenges on corticosterone levels and immunological indexes in the Broad-snouted Caiman (Caiman latirostris)

Abstract

In the wild, vertebrates face numerous unpredictable and harmful stressors such as storms, fires, earthquakes, tsunamis, and others. A typical physiological response to a perceived stressor is the increased secretion of glucocorticoids. Such a response is adaptive in the short term and could modulate the cellular immune response. Our purpose in this study was to examine the effect of stimulation with adrenocorticotropin (ACTH) injection and physical restraint (PR) on plasma corticosterone (CORT) levels, and total and differential white blood cell counts in the Broad-snouted Caiman (Caiman latirostris (Daudin, 1802)). Individuals under PR increased CORT levels over time. Otherwise, no differences were observed in the CORT concentration between individuals injected with ACTH and those injected with saline solution. High CORT concentrations in the PR caimans produced a biphasic profile on total white blood cell counts, as well as the lymphocyte and heterophil counts. This response to PR may represent a stress response with an increase in immune surveillance in organs.